> Algae needs solar light

Same with corn

> so you will have to flood a lot of land to get enough. Not necessarily, just use pre-existing water treatment plants to grow algae, and vertical photobioreactors exist. Algae also has a much higher harvest rate versus corn, and if you only wanted to ferment the algal biomass into corn you'd have much higher yields than corn.

> Also, in case of a war or blockade you can switch the corn use from ethanol to food. You will have to eat tortilla and polenta for a year [1] but it's better than algae from seawater or famine.

True

> Here we use sugar cane to produce etanol, it's more efficient because it's a C4 plant. I guess it's possible in the south of the US. Agreed.